The present invention relates to a thin film magnetic head mounted in a magnetic disk drive or the like for recording and reproduction and a method for manufacturing the same, particularly a method for manufacturing a write head.
As seen in a video recorder equipped with a hard disk drive and a hard disk drive built-in TV, needs for storing images and music in a hard disk drive are rapidly growing. Along with the expansion of the volume of image data, a higher areal recording density is required for a magnetic disk drive. Currently, when the bit length is made small in a thin film magnetic head, thermal fluctuations in the magnetization of a medium occurs, thereby making it impossible to increase the areal recording density. Therefore, technical shift from the current longitudinal recording to perpendicular magnetic recording which is rarely affected by thermal fluctuations is quickly proceeding in order to achieve an areal recording density of 100 Gbit/inch2 or more.
Low floatation is required for a perpendicular recording write head due to the reduced magnetic field strength caused by a reduction in track width like the high areal recording density. The major factor of preventing the low floatation of the magnetic head is a so-called “thermal protrusion phenomenon” (to be referred to as “TPR problem” hereinafter) that a head material for forming a device is warmed by the heat of a coil or static temperature and projects toward a medium. To cope with this TPR, JP-A No. 2004-134039 discloses that two layers of an organic insulator and of an inorganic insulator are used as coil insulating layers and lower and upper parts in contact with the inorganic insulator of the coil have the improved property of radiating heat generated by the coil.
As described above, the TPR problem that the device projects due to a rise in the temperature of the head and the static temperature and comes into contact with the medium is serious. The causes of this problem are (1) a rise in the temperature of the head by heat generated by applying a current to the coil (caused by the coil) and (2) a rise in the temperature of the head by the static temperature. For TPR caused by a coil current, the reduction of the resistance of the head is effective. To reduce the resistance of the head, the sectional area of the coil is increased. That is, a coil having a high aspect ratio must be formed to reduce the coil resistance. As a short magnetic path is effective for high-speed transfer, a coil having a high aspect ratio must be formed in a limited distance. However, a frame plating technique is currently used to form a coil and the height of a resist frame must be reduced to realize a narrow pitch. Since the film thickness of a coil must be at least 1.5 μm from the resistance value of a coil conductor at present, the minimum required thickness of a resist becomes 2.0 μm or more including a plating film thickness distribution. Therefore, it is difficult to reduce the height of the resist frame by the current forming technique.
For TPR caused by the static temperature that the magnetic material projects toward the medium due to a rise in the temperature of the head by the static temperature, there is no absolute countermeasure like TPR caused by the coil. It is merely said that the arrangement of a material having a low coefficient of thermal expansion in the magnetic head is effective according to calculation. However, it is desired to reduce this TPR caused by the environment. Thus the improvement of the head is desired to realize lower floatation.